Process of making flour.



No. 7|6,920. Patented Dec. 30, I902.

J. E. MITCHELL.

PROCESS OF MAKING FLOUR.

(Application filed Aug. 5, 1902.) (No Modai.) 2 Sheets-Shunt I.

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Inventor error OFFICE.

JOHN E. MITCHELL, OF ST. LOUIS, MISSOURI.

PROCESS OF MAKING FLOUR.

SPECIFICATION forming part of Letters Patent No. 716,920, dated December30, 1902' Application filed August 5,1902. Serial No. 118,537. (Nomodel.)

To all whom it may concern:

Be it known that I, J OHN E. MITCHELL, a citizen of the United States,residing at St. Louis, in the State of Missouri, have invented new anduseful Improvements in Processes of Making Flour, of which the followingis a specification.

My invention relates to improvements in the art of milling wheat-flour,the object of the same being to overcome the defects in the presentsystem of grinding and making the separations, and thereby produce afinished fiour of superior color and more even granulation and one whichhas greater strength and baking qualities.

The present method of producing flour by grinding and bolting consists,essentially, of two partsfirst, reducing the wheat on a series ofcorrugated rolls and separating the bran from the middlings, &c., bymeans of sieves or screens, and, second, purifying the middlings orgrits by air-currents and reducing the same to a fine flour by a seriesof re ductions on smooth rolls or other crushing or grinding devices.

My invention has to do altogether with an improvement in the latter partof the above process that is, the reduction of the middlings intoflour-and has no reference whatever to the first part, which, as stated,consists of grinding the wheat and separating the bran from theremaining portions.

The old or present method of converting the middlings into finishedflour consists, essentially, of crushing the purified middlings onsmooth rolls, making what is called the first reduction, and afterwardconveying or spouting the crushed product to a boltingreel orsifting-machine, where that portion of the product which has beenreduced fine enough for flour is bolted through a silk cloth of propermesh or degree of fineness. A very large portion of the product,however, which is not fine enough for finished flour passes over thesilk and is conveyed or spouted to another pair of rolls,where it isagain crushed, making what is called a secondreduction. The fine flourmade by this second reduction is separated in the same manner as before,the residue or unfinished part of the flour passing over the silkbolting-cloth to a third reduction, and so on, with as many reductionsas are necessary to reduce all the grits or sharp particles into flour.The residue passing over the sieve or bolting-cloth after the lastreduction has been made is supposed to be free from flour andflour-producing particles and to consist of woody fibrous materials,small bran-cuttings, and other impurities, usually termed the offal.

In order to produce the highest grade of flour economically, it isnecessary in operating a mill, first, to prevent any of the offal orother impurities from getting into the flour; second, to prevent anygood flour from passing offwith the offal, and, third, to produce afinished flour with a fine even granulation Without excessive grindingor other treatment that would impair-its strength or injure its bakingqualities. While these are three of the main objects the miller has inview, the present process of grinding and bolting referred to abovefails to a very great extent to accomplish any of said objects by reasonof the fact that it is impossible to make accurate or distinctseparations. To show that this is so, it is only necessary to refer tothe fact that the crushed product from any one of the series ofreductions consists practically of three distinct classes of stock -(a)that which is fine enough to be bolted into a finished flour of nearlyan even granulation; (b) the coarse gritty portion of the residue, whichrequires further reduction on rolls, and (c) an intermediate stockbetween the finished flour and the coarse hard stock which is too softto require further rolling or crushing and which is at the same time toorough to be bolted into the flour. According to my improved process thisintermediate product is separately ground by friction. It has been foundin practice that the'crushed product from any one of the reductionscontains a very large per cent. of this intermediate stock, which isbetween flour. of the proper fineness and the coarse particles whichneed further rolling or crushing, and according to the old process abovereferred to the operator is obliged either to let it pass through thesystem to the next succeeding reduction or bolt it through with thefinished flour by using a coarser or more open bolting-silk. When thisintermediate or partly-finished stock is allowed to continue on throughthe succeeding reduc- ICC tions, it is not only greatly injured byexcessive grinding, but it greatly interferes with the proper working ofthe rolls on the hard particles or that portion of the stock which doesneed further rolling or crushing. The result is that the reductions arevery uneven, and both a large portion of the soft intermediate stock andsome of the hard stock are finally passed off into feed with the ofial.The only way to avoid this loss according to the old process is to boltthe intermediate or partly-finished stock through with the flour inorder to keep the stock or residue going onto the rolls in propercondition; but when this is done the flour is greatly discolored anddefaced by the rough material which is bolted through with it and themarket value of the same materially decreased. To overcome this weakpoint in the present process of milling, I designed the mill disclosedin my Patent No. 617,345, dated January 10, 1899. The object of the millof said patent is to reduce the stock by friction or attrition, and ithas been used in connection with the rolls for reducing the middlings,the object being to useit alternately or on every' other reduction. Theprinciple of said mill was that it would only reduce or fiour the softstock, while the rolls would work largely on the hard round particles.This combination of rolls and frictiongrinders is still used veryextensively; but as each always has to operate upon more or less of thekind or class of stock which it is not capable of reducing or adapted toreduce into fiour the work of neither the rolls nor the frictiongrinderis wholly satisfactory. The combination of the two devices usedalternately on every other reduction has therefore only in a small wayovercome the objections above mentioned to the old process, the resultsbe ing nearly the same as when rolls were used alone. In either case thestock goes in a single stream or in a body through the series ofreductions and the residue from each reduction goes in a body to thenext succeeding reduction, and so on.

According to my improved process the middlings or unfinished residue iscarried through the system in two separate or parallel streams insteadofin a single stream, as in the old process, one stream containing allthe coarse or hard stock being crushed by rolls and the other streamcontaining the intermediate or soft stock being reduced by scrolls orother friction-grinders.

In the drawings forminga part of this specification two forms ofapparatus are shown by means of which my process may be carried intoefiect, Figure 1 showing diagrammatically an apparatus in whichbolting-reels are employed for making the separations, and Fig. 2showing diagrammatically a siftingmachine for making the separations.

According to Fig. 1 the first reduction is made, as shown, by smoothrolls 1 1 on the purified middlings, the crushed product going to ascalping-reel 2, which is .clothed with a coarse bolting-silk for thepurpose of scalping ofi or removing the coarse foreign matter. Theproduct passing through the bolting-silk of the scalpingreel 2 fallsinto the lion r-dressing'reel 3, the larger part of which is clothedwith a bolting-silk 4 of the proper degree of fineness to finish theflour uniformly which passes through it. The balance of the reel 3 isclothed with a somewhat coarser or more open silk 5, known as thetail-cloth, which lets through an intermediate stock that is hardly ofthe proper fineness and face to go with the finished flour, but is atthe same time entirely too soft to be handled successfully on the nextsucceeding rolls. The same has already been rolled sufficiently and onlyneeds to be reduced slightly or disaggregated to convert practically allof it into flour of the proper degree of fineness. For this purpose Iuse a scroll or other mill 6, that grinds by frictionfor example, oneconstructed in accordance with my Patent No. 617,345, heretoforereferred to-and after reducing this stock by such a mill it is sent tothe next succeeding sca1ping-reel7, similar in all respects to the reel2, heretofore referred to. The coarse stock or residue which passes overthe tail-cloth 5 of the dressingreel 3 contains the hard round particlesthat require further rolling, and being entirely free from any softmaterialit is in perfect condition for the rolls. This coarse stock isconveyed to and crushed upon the rolls 8 8, and the intermediate or softstock is reduced or disintegrated on the scroll-mill 6. The two streamsof material thus acted upon are then run together to the next succeedingscalping-reel 7 and thence to the next succeeding flour-dressing reel 9,where the separations are made in the same manner as before, and so onth rough the successive reductions until all the flour-producingparticles are converted into finished flour of practically the samedegree of fineness. The rolls 10 10 and 11 11 of the third and fourthreductions are substantially the same as the rolls 1 and 8, thescalping-reels 12 and 13 are of substantially the same construction asthe scalping-reels 2 and 7, and the flour-dressing reels 14 and 15 areof substantially the same construction as the corresponding reels 3 and9. The scalpings removed from the reels 2, 7, 12, and 13 are conveyedalong the lines indicated to a suitable dump or receptacle, and thefinished flour, which passes through the dressing-reels 3, 9, 14:, and15, passes along the lines indicated to a common receptacle. The fiouris taken out after each succeeding reduction through silk of the propermesh to insure its uniformity and freedom from impurities, and theresidue before each succeeding reduction is separated into two separatestreams, the coarse hard stock going to crushing-rolls and the softintermediate stock going to scrolls or friction-disaggregating mills.According to this process fewer reductions are necessary and but half asmuch roll-surface is required as according to the old system. Thefinished flour can easily be kept free from otl'al and other impurities,and the oifal can be kept free from the flour. As the two streams ofstock are always in perfect condition for the kind of mill used fortheir reduction, the reduction is done easily and without injury to thestrength or baking qualities of the flour.

As above stated, Fig. 2 of the drawings shows diagrammatically theapplication of my improved process to a sieve system of bolting. Therolls 1, 8, 10, and 11 and the friction disaggregating devices 6 are thesame as the corresponding parts shown in Fig. 1. The separations aremade in substantially the same manner as according to the apparatusshown in Fig. 1, except that instead of the scalping-reels andflour-dressing reels a series of flat sieves are employed. The uppersieve 16 of each set of sieves being clothed with a coarse open silkconstitutes the scalper, the coarse particles from which pass along thelines indicated to the common dump or receptacle. The stock passingthrough the sieve 16 is conveyed, as shown by arrows 17, over a seriesof sieves 19,0lothed with fine silk, through which the Hour passes, thelast or lowermost sieve 19 being clothed with a more open silk to letthrough the soft intermediate stock, which goes to the scroll 6. Beneatheach of the sieves 19 is an imperforate bottom, which receives the flourwhich passes through said sieves 19 and from which bottom the finishedflour passes along the lines indicated to a com; mon receptacle. Thehard coarse stock pass-- ing over the last sieve 19 is conveyed, asindicated by the arrows 20, to the crushing-rolls of the next succeedingreduction. After the two streams are reduced on the rolls 8 and on thefriction disaggregating device 6 they run together, as shown, and go tothe next series of sieves, where theseparations are repeated, and so onas before. The residue after the Hour is taken out is always separatedin two streams, the coarse hard particles going to the crushing-rollsand the intermediate or soft particles to frictional disaggregatingdevices.

Having described my invention, what I claim as new, and desire to secureby Letters Patent, is-

1. The process of making flour, which consists in crushing or grindingthe middlings, by rolls, screening the same to remove the flour andseparate the same from the coarser particles and to simultaneouslydivide the latter into two masses, one containing the hard coarseparticles that require further crushing and the other containing thesoft fine particles that do not require further crushing, subjecting thehard particles in one mass to a further crushing, by rolls,disaggregating the soft particles in the other mass by friction,screening the two masses together after they have been thus treated, toremove the flour and separate the same from the coarser particles, andto simultaneously divide the latter into two masses, and proceeding asbefore with said two masses through one or more successive reductions.

2. The process of making flour from purified middlings, by two or moresuccessive reductions, which consists in crushing or grinding themiddlings, screening the same to separate and remove any coarse foreignmatter, screening the remaining portion to remove the flour and separatethe same from the coarser particles, and to simultaneously divide thelatter into two streams, one containing the coarse hard particles thatrequire further crushing and the other containing the soft fineparticles that do .not require further crushing, subjecting the streamcontaining the hard particles to a further crushing, by rolls,disaggregating the soft fine particles in the other stream, by friction,uniting the two streams after they have been thus treated, screening theunited mass to remove the flour, and separate the same from the coarserparticles, and to simultaneously divide the latter into two streams, andproceeding as before with said two streams through one or moresuccessive reductions.

In testimony whereof I have hereunto set my hand in presence of twosubscribing witnesses.

JOHN E. MITCHELL.

